论文标题
吸收托里星星的磁性倾斜
The magnetic obliquity of accreting T Tauri stars
论文作者
论文摘要
经典的T Tauri恒星（CTTS）通过其磁层从其圆盘中增添了材料。积聚流的几何形状在很大程度上取决于磁性斜率，即旋转轴和磁轴之间的角度。我们的目的是在10个CTTS样品中得出磁性倾斜的分布。为此，我们监视了这些恒星光谱沿其旋转周期中HEI $λ$ 5876线的径向速度变化。 HEI在积聚冲击中产生，靠近磁极。当磁轴和旋转轴未对齐时，该线的径向速度会通过恒星旋转来调节。调制的幅度与恒星投影的旋转速度，$ v \ sin i $和热点的纬度有关。通过从光谱中得出$ v \ sin i $和hei $λ$ 5876径向速度曲线，我们因此获得了磁性斜率的估计。我们在11.4 $^{\ circ} $的样本中找到平均倾斜度，RMS分散剂为5.4 $^{\ circ} $。因此，磁轴似乎几乎是，但与这些吸收的tauri恒星中的旋转轴并不完全一致，在某种程度上与光谱极化的研究有些分歧，这些研究发现了几个CTTSS的磁性轴。这可能仅仅是数量统计数字较低的效果，也可能是由于我们样本的选择偏差所致。我们讨论了我们的样本可能受到的可能偏见。我们还发现暂定的证据表明，磁倾斜可能会根据恒星内部而变化，并且完全对流和部分辐射恒星之间可能存在显着差异。
Classical T Tauri stars (CTTS) accrete material from their discs through their magnetospheres. The geometry of the accretion flow strongly depends on the magnetic obliquity, i.e., the angle between the rotational and magnetic axes. We aim at deriving the distribution of magnetic obliquities in a sample of 10 CTTSs. For this, we monitored the radial velocity variations of the HeI$λ$5876 line in these stars' spectra along their rotational cycle. HeI is produced in the accretion shock, close to the magnetic pole. When the magnetic and rotational axes are not aligned, the radial velocity of this line is modulated by stellar rotation. The amplitude of modulation is related to the star's projected rotational velocity, $v\sin i$, and the latitude of the hotspot. By deriving $v\sin i$ and HeI$λ$5876 radial velocity curves from our spectra we thus obtain an estimate of the magnetic obliquities. We find an average obliquity in our sample of 11.4$^{\circ}$ with an rms dispersion of 5.4$^{\circ}$. The magnetic axis thus seems nearly, but not exactly aligned with the rotational axis in these accreting T Tauri stars, somewhat in disagreement with studies of spectropolarimetry, which have found a significant misalignment ($\gtrsim 20^{\circ}$) for several CTTSs. This could simply be an effect of low number statistics, or it may be due to a selection bias of our sample. We discuss possible biases that our sample may be subject to. We also find tentative evidence that the magnetic obliquity may vary according to the stellar interior and that there may be a significant difference between fully convective and partly radiative stars.
